"Overpopulation is a major concern for the future of Brazil, China and the entire world because of its adverse effects on the health and well-being of humans resulting from poverty, malnutrition, disease, environmental pollution and destruction of natural resources. We address the overpopulation problem through biological research to develop a new and effective method for male contraception.[unreadable] The Laboratories for Reproductive Biology at the University of North Carolina School of Medicine at Chapel Hill is participating in an international collaborative network together with the following foreign laboratories: 1) Section of Experimental Pharmacology, Department of Pharmacology, Escola Paulista de Medicina, Universidade Federal de Sao Paulo, Brazil, 2) Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute for Biological Sciences and 3) The Laboratory of Reproductive Medicine, Department of Urology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China. [unreadable] Network activities include: 1) research collaborations 2) research training for predoctoral and postdoctoral students 3) exchange visits by participating faculty members and trainees for research discussions, seminars, and workshops. [unreadable] The program will produce new investigators and advances in research to increase our knowledge of how spermatozoa acquire fertilizing ability and will use this information to develop a new and improved method of male contraception. [unreadable] Ultimately, the goal of our research is to help solve the global problem of overpopulation and its multiple adverse effects on the health and well being of humans.[unreadable] "[unreadable] [unreadable] [unreadable] [unreadable] [unreadable]